java - Get 12 hours before and after current time

Question

I'm having an issue working with time in Java. I don't really understand how to efficiently solve comparing the time of now and 12 hours before and after

I get a set of starting times for a show from an API and then compare that starting time with LocalTime.now(). It looks something like this:

SimpleDateFormat sdt = new SimpleDateFormat("HH:mm:ss");
String temp = sdt.format(Local.time(now));
LocalTime secondTime = LocalTime.parse(parts1[0]);
LocalTime firstTime = LocalTime.parse(temp);
int diff = (int) ((MINUTES.between(firstDay, secondDay) + 1440) % 1440);
if(diff <= 720){
    return true;
}

Where my idea is that if the difference between the two times is smaller than 720 minutes (12 hours) I should get the correct output. And this works for the 12 hours before now. I thought I might need to swap the parameters of .between, to get the other side of the day. That counts it completely wrong (If the time now is 15:00:00 it would accept all the times until 22:00:00 the same day). Is this just a really bad way of comparing two times? Or is it just my math that lacks understanding of what I'm trying to do?

Thanks

Answer 1

Using the 'new' (not that new) Java 8 time API:

Instant now = Instant.now();
Instant hoursAfter = now.plus(12, ChronoUnit.HOURS);
Instant hoursBefore = now.minus(12, ChronoUnit.HOURS);